4 * Here, we have (n, k) code with rate R = k / n.* If the symbol is either 0 or 1 >>> Binary block code, symbols are named bits.* There are 2^n possible code words in a binary block code of length n.* From these, we choose 2^k code words to be mapped to M = 2^k different message.* Thus, a block of k information bits is mapped into a code word of length n selected from the set M = 2 ^ k code words.* Any code has a weight which is the number of nonzero elements that it contains.

5 (measure of difference between any two code words)* Hamming distance is the number of differences between the corresponding elements in any two code words.(measure of difference between any two code words)Ex. dh (1100,1111) = 2dh (1100,1101) = 1Then 1100 is closer to 1101* The smallest hamming distance between any two code words is called the minimum hamming distance dh min.* The idea with error correction codes is to pick the 2^k code words of the 2^n total possible code words which are far enough apart (in terms of Hamming distance) to guaranteeyou are able to correct a certain number of errors.* dh min = 2*Ct + Dt +1

6 Linearity:* The block code is called linear block code if the addition of any two code words is also a code word.* The addition is performed under Galois Field GF(2) in binary block code.*Linearity implies that the linear block code must contain the all zeros code word.